Heat exchanger

ABSTRACT

A heat exchanger for performing heat exchange of a medium by heat conducted to tubes ( 210 ) and fins ( 220 ), the heat exchanger is configured by assembling the tubes, the fins, tanks ( 300 ) and a connector ( 400 ) and heating them in a furnace to be brazed into one body, wherein the connector is made of aluminum or its alloy and has a seating face to be brazed to the outer surface of the tank, and when it is determined that the connector has a surface area of X [cm 2 ] and a volume of Y [cm 3 ], they have a relation of X≧1.5·(36πY 2 ) 1/3 , Y≦30.

TECHNICAL FIELD

[0001] The present invention relates to a heat exchanger which iscomprised of tubes for flowing a medium, fins attached to the tubes,tanks to which ends of the tubes are connected, and connectors disposedon the tanks, and performs heat exchange of the medium by heat conductedto the tubes and the fins.

BACKGROUND ART

[0002] A heat exchanger such as a condenser of a refrigeration cycle ora radiator of automobiles is configured by alternately stacking aplurality of tubes and a plurality of fins to form a core and connectingends of the tubes to the tanks. A medium is introduced into the insidethrough one of connectors disposed on the tank, flowned through thetubes while performing heat exchange with heat conducted to the core,and discharged to the outside from the other connector disposed on thetank.

[0003] Generally, this type of heat exchanger is produced by assemblingthe tubes, fins, tanks and connectors and heating the assembly to brazeinto one body in a furnace. And, to braze in the furnace, a brazingmaterial and flux are previously disposed on required potions of therespective members.

[0004] To heat in the furnace, it is important that the respectivemembers are heated as uniformly as possible so to braze the entire heatexchanger uniformly.

[0005] In this connection, the connectors have a disadvantage that heatconduction is quite slow and it takes time to braze as compared with thetubes and the fins which are formed to be thin.

[0006] The present invention was achieved in view of the above-describedcircumstances, and an object of the invention is to provide a heatexchanger which can have the connectors brazed efficiently.

DISCLOSURE OF THE INVENTION

[0007] The invention described in Claim 1 is a heat exchanger whichcomprises tubes for flowing a medium, fins mounted on the tubes, tanksto which the ends of the tubes are connected and connectors disposed onthe tanks, and performs heart exchange of the medium by heat conductedto the tubes and the fins, wherein the heat exchanger is formed byassembling the tubes, the fins, the tanks and the connectors and heatingthem in a furnace to braze into one body, the connectors are made ofaluminum or its alloy and having a seating face to be brazed to theouter surface of the tanks, and when it is assumed that the connectorshave a surface area of X [cm²] and a volume of Y [cm³], they are:

X≧1.5·(36πY ²)^(1/3)  {circle over (1)}

[0008] Y≦30 . . . {circle over (2)} and, the connectors are brazedefficiently by configuring as described above. Its concept will bedescribed below.

[0009] First, the connectors conduct heat very slowly as compared withthe tubes and the fins which are formed thin, so that heat transmissionis improved by securing a large surface area against a volume.

[0010] Here, when it is assumed that a certain object has a surface areaX and a volume Y, a shape having minimum X against Y is a sphere. And,when it is assumed that the sphere has a radius r, they are in thefollowing relationship:

X=4πr ²  {circle over (3)}

Y=4πr ³/3  {circle over (4)}

[0011] when r is removed from the expressions {circle over (3)} and{circle over (4)}, the result is:

x=(36πY ²)^(1/3)  {circle over (5)}

[0012] where, π is the ratio of the circumference of a circle to itsdiameter.

[0013] And, the present invention determines the surface areas of theconnectors to 1.5 times or more a sphere based on the surface area ofthe sphere having a volume equal to that of the connectors as astandard. Therefore, the surface area of the connector is 1.5 times ormore the right side of the expression {circle over (5)} and indicated bythe expression {circle over (1)}.

[0014] The upper limit of the volume of the connector is determined tobe 30 [cm³] as indicated by the expression {circle over (2)}.Specifically, the surface area is proportional to the square of thediameter, and the volume is proportional to the cube of the diameter.Therefore, brazing of the connector becomes disadvantageous as itsvolume becomes larger. Thus, the volume of the connector is determinedto have the above-described upper limit to adequately secure the brazingproperty.

[0015] When it is assumed that one side of a cube is a, the surface areaand the volume have the following relationship:

X=6a ²  {circle over (6)}

Y=a ³  {circle over (7)}, and

[0016] when a is removed from the expressions {circle over (6)} and{circle over (7)}, the result is X=6Y^(2/3) . . . {circle over (8)}.According to the expressions {circle over (5)} and {circle over (8)},the surface area of the cube becomes approximately 1.24 times that of asphere having the same volume.

[0017] In addition, this type of conventional connector, namely aconnector having a seating face to be brazed to the outer surface of thetank, having a volume of 30 [cm³] or less, was sampled in plurality oftypes, and the samples were measured for a ratio of surface area againstthose of spheres having the same volumes. It was found that the ratiosof surface area were somewhat larger than the above-described 1.24times, namely approximately 1.3 to 1.45 times.

[0018] Specifically, the numerical value 1.5 times or more theexpression {circle over (1)} is determined considering the conventionalconnector, and it falls in a range to improve the heat transmission ofthe connector without fail. And, such a numerical value is considered tobe more preferably 1.8 times or more.

[0019]FIG. 7 is a correlation graph of a surface area and a volume. Inthe drawing, values of a surface area and a volume of the connectoraccording to the invention are indicated in a hatched area A.

[0020] The invention described in Claim 2 relates to the heat exchangeraccording to Claim 1, wherein the connector is provided with a pipesection which is protruded from the seating face for insertion into thetank.

[0021] By configuring as described above, the connector is accuratelydisposed by inserting the pipe section into the tank.

[0022] The invention described in Claim 3 relates to the heat exchangeraccording to Claim 1 or 2, wherein the connector is provided with abolt-attaching section for screwing or inserting a bolt for connectionof an outer passage.

[0023] By configuring as described above, the connector and the outerpassage are connected with a bolt, and airtightness and support strengthare secured without fail.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a front view showing a heat exchanger according to anembodiment of the invention.

[0025]FIG. 2 is an exploded perspective view showing a tank and a coreaccording to the embodiment of the invention.

[0026]FIG. 3 is an explanatory diagram showing a tank and a connectoraccording to an embodiment of the invention.

[0027]FIG. 4 is a front perspective view showing an inlet connectoraccording to an embodiment of the invention.

[0028]FIG. 5 is a rear perspective view showing the inlet connectoraccording to the embodiment of the invention.

[0029]FIG. 6 is a perspective view showing a connector for connection ofa gas-liquid separator according to an embodiment of the invention.

[0030]FIG. 7 is a correlation graph of a surface area and a volume.

BEST MODE FOR CARRYING OUT THE INVENTION

[0031] Embodiments of the present invention will be described in detailbelow with reference to the accompanying drawings.

[0032] A heat exchanger 1 of this embodiment is a radiator of arefrigeration cycle for car air conditioner mounted on automobiles andprovided with a core 200 formed by alternately stacking a plurality oftubes 210 for flowing a medium (namely a refrigerant) and a plurality offins 220 and a pair of tanks 300 to which both ends of the tubes 210 areconnected as shown in FIG. 1 to perform heat exchange of the medium byheat conducted to the core 200.

[0033] Such a refrigeration cycle is to circulate a CFC-based medium andprovided with a compressor for compressing the medium, a radiator forcooling the compressed refrigerant, an expansion valve for decompressingthe cooled refrigerant, and an evaporator for evaporating thedecompressed refrigerant. Specifically, the heat exchanger 1 of thisembodiment as the radiator is a condenser which cools the medium andcondenses from a gas layer to a liquid layer.

[0034] The tanks 300 are provided with an inlet connector 400 forintroducing the medium and an outlet connector 500 for discharging themedium.

[0035] The medium is flowed into the tank 300 through the inletconnector 400, flowed through the tubes 210 while performing heatexchange and discharged to the outside of the tank 300 through theoutlet connector 500.

[0036] The respective tanks 300 are divided their interiors atprescribed intervals, so that the medium is made to reciprocate aplurality of times between the tanks 300.

[0037] A side plate 600 is disposed as a reinforcing member on the topand bottom sides of the core 200. Ends of the respective side plates 600are supported by the tanks 300.

[0038] Besides, one of the tanks 300 is provided with a gas-liquidseparator 700. The medium, while flowing from the inlet connector 400 tothe outlet connector 500, is first sent from the tank 300 to thegas-liquid separator 700 and only the liquid layer is sent to the outlet500.

[0039] The tank 300 and the gas-liquid separator 700 are mutuallyconnected via a connector 800 for connection of the gas-liquid separatorwhich is disposed on the side of the tank 300.

[0040] The tubes 210, fins 220, tanks 300, inlet connector 400, outletconnector 500 and side plates 600 configuring the heat exchanger 1 areformed of aluminum or aluminum alloy, and such members are assembled andthe assembly is heated in a furnace to form one body. The brazingmaterial clad and flux are previously applied to the necessary portionsof the respective members.

[0041] Especially, the tubes 210 of this embodiment are formed to beflat by extrusion forming or roll forming of a plate. Their insides aredivided into a plurality of sections in order to obtain the requiredpressure resistance.

[0042] The tanks 300 of this embodiment each is configured by assemblinga tank plate 310 and an end plate 320 as shown in FIG. 2.

[0043] The tank plate 310 and the end plate 320 are formed bypress-forming a plate of aluminum or aluminum alloy having a prescribedthickness.

[0044] The tank plate 310 is a semicircular cylindrical member, and theend plate 320 is a member provided with holes 321 into which the ends ofthe tubes 210 are inserted for connection. The holes 321 of the endplate 320 are disposed in plural numbers at prescribed intervals alongthe longitudinal direction of the end plate 320.

[0045] Partition plates 330 are disposed between the tank plate 310 andthe end plate 320 with prescribed intervals. Specifically, the ends andinterior of the tank 300 are closed and divided by the partition plates330.

[0046] In this embodiment, the tank plate 310 and the end plate 320 areassembled with the end plate 320 fitted to both edges of the tank plate310. And, both edges of the end plate 320 are brazed to the innerperiphery of the tank plate 310.

[0047] Besides, edges 310 a of the tank plate 310 are formed a pluralityof bending pieces 311 for holding the end plate 320 with appropriateintervals.

[0048] The end plate 320 is positioned on the tank plate 310 and fixedby bending the bending pieces 311. The bending pieces 311 are bent by acaulking jig or the like.

[0049] The inlet connector 400 is a block-shaped member which is formedby machining aluminum or its alloy into a prescribed shape and has apipe section 410 which is inserted into the tank plate 310, a curvedseating face 420 which is fitted to the outer surface of the tank plate310, a connection section 430 for connecting an outer passage, and abolt fitting portion 440 for screwing or inserting a bolt for connectionof the outer passage as shown in FIG. 3 to FIG. 5. The pipe section 410is protruded from the seating face 420.

[0050] And, the inlet connector 400 is disposed by inserting the pipesection 410 into the hole 312 formed in a required portion of the tankplate 310, brazing the pipe section 410 to the hole 312 and brazing theseating face 420 to the outer surface of the tank plate 310.

[0051] The pipe section 410, which is inserted into the hole 312 of thetank plate 310, has its leading end partly expanded. By expanding theleading end of the pipe section 410, the pipe section 410 is preventedfrom coming out, and the medium is flowed smoothly.

[0052] The tank plate 310 and the end plate 320 are assembled afterinserting the pipe section 410 of the connector 400 into the tank plate310.

[0053] In this embodiment, the inlet connector 400 has a surface area of35 [cm²] and a volume of 5.5 [cm³]. And, aluminum or its alloy have aspecific gravity of approximately 2.7 [g/cm³], and the connector 400weighs approximately 15 [g].

[0054] And, when the connector 400 is determined to have a surface areaof X [cm²] and a volume of Y [cm³],

[0055] 1.5·(36πY²)^(1/3)≈22.6,

[0056] X≧1.5·(36πY²)^(l/3), and

[0057] Y≦30 is established.

[0058] Therefore, the inlet connector 400 can be brazed efficiently bybrazing in a furnace.

[0059] The relationship between the surface area and the volume dependson the structure, appearance and design of the connector 400, and theconnector 400 is designed based on such a configuration.

[0060] On the other hand, the outlet connector 500 has a surface area of21 [cm²] and a volume of 3.1 [cm³]. And, the connector 500 weighsapproximately 8.4 [g]. The other structure is the same as the inletconnector 400 and, therefore, its description is omitted.

[0061] When it is determined that the connector 500 has a surface areaof X [cm²] and a volume of Y [cm³],

[0062] 1.5·(36πY²)^(1/3)≈15.4,

[0063] X≧1.5·(36πY²)^(1/3), and

[0064] Y≦30 is established.

[0065] Therefore, the outlet connector 500 can also be brazedefficiently by brazing in a furnace.

[0066] Besides, a connector 800 for connection of a gas-liquid separatorof this embodiment is a block member formed by machining aluminum or itsalloy into a prescribed shape and has one passage for flowing the mediumfrom the tank 300 to the gas-liquid separator 700 and the other passagefor flowing the medium from the gas-liquid separator 700 to the tank300.

[0067] Specifically, the connector 800 has a seating face 820 which isbrazed to the outer surface of the tank 300, a first pipe section 811which is protruded from the seating face 820 to provide an inlet end ofone passage into the tank 300, and a second pipe section 812 which isprotruded from the seating face 820 to provide an outlet end of theother passage into the tank 300 as shown in FIG. 6.

[0068] The brazing area between the seating face 820 and the tank 300 iswidened by flanges 821 formed on the required portions of the connector800.

[0069] The tank plate 310 is formed with holes into which the first pipesection 811 and the second pipe section 812 are inserted.

[0070] Specifically, the connector 800 for connection of the gas-liquidseparator has the first pipe section 811 and the second pipe section 812protruded from the seating face 820 and inserted into the holes of thetank plate 310, the first pipe section 811 and the second pipe section812 brazed to the holes by brazing in a furnace, and the seating face820 brazed to the outer surface of the tank 300 to secure airtightnesswith the tank 300 and a supporting strength to the tank 300.

[0071] Besides, one of the above-described partition plates 330 isdisposed between the hole into which the first pipe section 811 isinserted and the hole into which the second pipe section 812 is insertedin the tank 300.

[0072] And, this connector 800 is provided with a bolt attaching section840 for insertion of a bolt, and the gas-liquid separator 700 is formedwith a female thread section for screwing the bolt. The gas-liquidseparator 700 is attached by screwing the bolt which is inserted intothe bolt attaching section 840 into the female thread section.

[0073] When the gas-liquid separator 700 is attached, the outlet end ofone passage is connected to the inlet section of the gas-liquidseparator 700 through a third pipe section 831, the inlet end section ofthe other passage is connected to the outlet section of the gas-liquidseparator 700 through a fourth pipe section 832.

[0074] The connector 800 for connection of the gas-liquid separator hasa surface area of 60 [cm²] and a volume of 15.6 [cm³]. And, theconnector 800 weighs approximately 42 [g].

[0075] When the connector 800 has a surface area of X [cm²] and a volumeof Y [cm³],

[0076] 1.5·(36πY²)^(1/3)≈45.3,

[0077] X≧1.5·(36πY²)^(1/3), and

[0078] Y≦30 is established.

[0079] Therefore, the connector 800 for connection of the gas-liquidseparator can be brazed efficiently by brazing in a furnace.

[0080] The relationship between the surface area and the volume dependson the structure, appearance and design of the connector 800, and theconnector 800 is also designed based on the above configuration.

[0081] As described above, in the heat exchanger of this embodiment, theinlet connector 400, the outlet connector 500 and the connector 800 forconnection of the gas-liquid separator can be efficiently brazed to thetanks 300, and a rationalization of its production was achieved.

[0082] The heat exchanger 1 of the embodiment is a condenser forcondensing the medium from a gas layer to a liquid layer, and thestructures of the inlet connector and the outlet connector can also beapplied to, for example, an evaporator, a radiator and another heatexchanger.

[0083] Especially, there is a refrigeration cycle adopting CO₂ as amedium in recent years, and its radiator's inside pressure exceeds thecritical point of the medium depending on the use conditions such as atemperature. The critical point is a limit of a high temperature withthe coexistence of the liquid layer and the gas layer, namely, of thelimit on the side of high pressure.

[0084] And, when used as a radiator of such a refrigeration cycle, theinner pressure becomes very high, and, therefore a compressive strengthof each member is improved by decreasing a passage area of the tanks ortubes for the refrigerant or increasing the thickness of the tank plateand the end plate.

[0085] The heat exchanger of this embodiment is preferably used for aradiator of such a refrigeration cycle.

INDUSTRIAL APPLICABILITY

[0086] The present invention is a heat exchanger generally used for arefrigeration cycle of a car or home air conditioner, and especiallysuitable for a refrigeration cycle which uses, for example, CO₂ as arefrigerant and having a pressure in the radiator exceeding the criticalpoint of the refrigerant.

1. A heat exchanger which comprises tubes for flowing a medium, fins mounted on the tubes, tanks to which the ends of the tubes are connected and connectors disposed on the tanks, and performs heart exchange of the medium by heat conducted to the tubes and the fins, wherein: the heat exchanger is formed by assembling the tubes, the fins, the tanks and the connectors and heating them in a furnace to braze into one body, the connectors are made of aluminum or its alloy and have a seating face to be brazed to the outer surface of the tanks, and when it is assumed that the connectors have a surface area of X [cm²] and a volume of Y [cm³], they are X≧1.5·(36πY ²)^(1/3), then Y≦30.
 2. The heat exchanger according to claim 1, wherein the connector is provided with a pipe section which is protruded from the seating face for insertion into the tank.
 3. The heat exchanger according to claim 1 or 2, wherein the connector is provided with a bolt attaching section for screwing or inserting a bolt for connection of an outer passage. 